1. Field of the Invention
The present invention relates generally to fuel injection for engines of automotive vehicles, and more particularly to, a method for firing a fuel injector on an engine of an automotive vehicle.
2. Description of Related Art
Typically, an engine of an automotive vehicle has one or more fuel injectors for delivering fuel from a fuel source to cylinders of an internal combustion engine. Generally, a sensor on a distributor of the engine transmits a signal from the distributor as to the crank angle of the engine. This distributor reference signal is received by an electronic control unit (ECU) which outputs a signal to fire the fuel injectors at predetermined states of the distributor reference signal. One predetermined state may be a "zero degree" or "falling" edge of the distributor reference signal as illustrated by reference letter A in FIG. 1. Previously, these fuel injectors were fired in pairs, e.g. two at a time, at the predetermined state. This type of fuel injection is termed "two-group" or "banked" fuel injection.
Fuel injector firing at the zero degree edge of the distributor reference signal is optimum for peak performance of the engine (e.g., open throttle, vehicle moving). However, fuel injector firing may occur at another predetermined state. This predetermined state may be an "eighty-three (83) degree" or "rising" edge of the distributor reference signal as illustrated by reference letter B in FIG. 1. Fuel injector firing at the eighty-three degree edge of the distributor reference signal is optimum for idle quality (e.g., closed throttle, vehicle not moving). The fuel injectors may be fired sequentially, e.g. one at a time, at the predetermined states. This type of fuel injection is termed "bi-modal sequential" fuel injection.
One problem that occurs in fuel injection timing is the transfer from one predetermined state to another predetermined state for firing the fuel injectors; that is, the transfer from the zero degree edge to the eighty-three edge of the distributor reference signal for firing the fuel injectors in bi-modal sequential fuel injection. This problem results in a lean engine operating condition. Moreover, a closed throttle bucking/engine RPM undershooting may result from the lean engine operating condition any time a transfer from open to closed throttle occurs.